Nerve growth factor (NGF) enhances the growth and differentiation of sensory and sympathetic ganglia. The mechanism by which this occurs, however, is just beginning to be uncovered. The purpose of the project is to determine what the molecular species of mouse submaxillary gland Beta NGF and 7S NGF at physiological concentrations, to determine where the active site or portion of the Beta NGF molecule is and to compare snake venom NGF to Beta NGF. The molecular species present at physiological concentrations for 7S NGF and Beta NGF will be determined by the use of Sephadex gel filtration and polyacrylamide gel electrophoresis. The species present in the sera of various mammals will be determined by reaction with purified antibodies to cross-linked 7S NGF and to the individual subunits. The active site of the Beta NGF molecule will be determined by looking at the fragments which remain after proteolytic cleavages which either decrease the biological activity of NGF of eliminate it completely. The types of interactions of snake venom NGF with the alpha and gamma subunits of 7S NGF will be determined. The binding constants of snake venom NGF to the NGF receptor of embryonic chick dorsal root will also be determined and compared to those obtained for Beta NGF.